For example, Patent Document 1 discloses a lumbar support for an automobile in which a torsion bar formed in a substantially U-shape is used, an upper arm part of the torsion bar is supported by a seat frame, and a middle arm part and a lower arm are supported by a plate for support. A support pressure by the plate for support is adjustable by adjusting a front and back position of the upper arm part. Horizontal oscillation of the plate for support is eliminated by providing the middle arm part and the lower arm part. The feeling during seating is improved by preventing center shift of the plate for support. Patent Document 2 discloses a structure in which a support member formed of a seat-shape member such as a cloth and a rubber is stretched in a portion corresponding to a lumbar part of a seated person by using a coil spring. In this support member, a fixed support member and an adjustable support member of which extension can be adjusted by tensioning and loosening by length adjustment, are arranged in lamination, the fixed support member exhibits a fundamental support pressure of a lumbar part of a seat back, and the adjustable support member has functions of back-up at a time of breakage of the fixed support member and adjustment of a support pressure of a top part.